Manufacture of manganese steel.



facture of Manganese Steel;

'ing ladle, or like WINFIELD S. POTTER,

orrioE j on NEW Yo'aK,

MANUFACTURE OF MANGANESE STEEL.

N 0 Drawing.

Specification of Letters Patent. Application filed June 18, 1910.

Serial No. 567,696.

To all whom it may concern:

Be it known that I, Winrlnno S. Porran, I a citizen of the UnitedStates, residing in the city and State of New York, and whosepost-olfice address is 30 Church street, New York city, New York, haveinvented certain new and useful Improvements in the Menuand I doherebydeclare the followin to be a full, clear, and exact description ofthe invention, such as Will enable others skilled in the art to which itappertains to make and use the same.

In an application forLetters Patent of the United btates, filed by meunder date of May 20, 1910, Serial 0. 562,374, I have described andclaimed the production of a manganese steel ingot, devoid of dendritesand other objectionable freezing structures and of a strong uniform finegrained structure throughout by a series of steps beginning with thetreatment of the molten metal itself before the ingots are cast, andcontinuing with the subsequent reconstruction of theingot desirable foradapting it toasuccessful commercial rolling, forging or shap- H10. isbroadly set forth in my application" referred to, the fundamentaldiscovery emf bodied therein was, that by suitably deoxi-' dizing andcleansing the molten metal as described, while still in the furnace,castsource of supply, it is possible to standardize the subsequent heattreatment of the cast ingot, and, particula'rly, for steel of any givencomposition, to practically eliminate variations. in tliatrpart of theheat treatment of the termines the reconstruction of thedendriticportion and its conversion into the strong uniform fine grainedstructure desired. .The invention, as described in mysaid'application,involved the furtherdiscovery, that the preliminary deoxidation andcleansing of the metal has the functionof establish ing a practicallydefinite and short period of time for the. complete conversion ofthedendrites and the removal ofthe other -objectionable freezingstructures, therebyx V-enabling the operator to promptly terminate thatstage of the heat treatment,- which would otherwise tend to theformation and building upiof large and coarse-crystals, or

grains. n The present application, which is based upon the samefundamental features of discovery above noted, is directed specificallyI f to a particular method ingot which desecured -theladle itself andWith for carrying out the general operation and for realizing its char:acteristic advantages.

-More particularly stated, this specific en1'-- invention involves, the

bodiment of the general operation, the feature-of preventing theformation and building up of large and coarse crystals of grains, .bylowering the Patented Aug. 30, 1919,

temperature of the outer portions of the in 5 got, after theobjectionable freezing structures have been removed and thedesiredreconstruction into metal of uniform fine grain has beenaccomplished.

It also includes the-further.feature of supplementing this lowering ofthe temperature of the outer portions of the ingot for additionalcondition in which it then finds itself, to

receive, by light rolling, the tough thick skin contemplated. v p

The preliminary treatment of the metal, includingthe compoundingthereof, is fully set forth in its application for Letters Patent of theUnited States hereinbefore referredto, wherein it is assumed that, inthe particular instance given, the manganese. steel is to, be 1compounded from suitably dephosphorized and desulfurized open hearthsteel from aniopen hearth furnace, and molten ferro-manganese, mixed inthe desired. ladleof large capacity or other suitable containerappropriate for the purpose. v The operations of compoundingthe metal,deo xizdizmg' and cleansing, 1t,

, ay, oweve be effected in theopen hearth-or like furnace itself,although, in thecase of thishveryread- 11y oxidized inetal,the mostcomplete deoxi dizing, cleansing and washing can only be by continuingthose operations in the employment of a protective cover of acid slag,as lierein- .aft'er'described' I I that. the compounding of the Assumingmetal is to be effected inthecastmg ladle of large capacit (say sixtytens .or more) the ladle will bellined with the usual silicious or acidlining, preheated in the customary proportions in "a casting preferredembodiment, in my" to obtain such acid slag formed 'dients such assodium silicate,lime,

manner The charge of dephosphorizcd molten steel from the open hearth orlike furnace will then be run into the ladle and simultaneouslytherewith the molten ferromanganese will likewise be charged therein. IAs the charge of molten metal rises in the ladle, it is essential forthe purpose of the invention to maintain upon its upper surface aprotecting layer of acid slag. F or this purpose, the ladle may, ifdesired,be charged with a small quantity of readily fusible acid slagmaking materials, or a mixture which will form a readily fusible acidslag, before the steel is running from the furnace; or in lieu thereof,or in addition thereto, the acid slag making material may be added fromtime to time to the charge, as thelevel of the metal rises in the ladle.The acid slag making materials may conveniently consist of silica orother silicious material associated with a sufficient amount of tiuxingingreor lead oxid, to make it readily fusible at a sufficiently lowtemperature, and the proportion of silica should be sufiicientto balancethe oxids present in the steel, (as, for instance, the oxid of iron andoxid of manganese) which it is the purpose of my invention-to eliminate,as far as possible, by the treatment proposed. The purpose of chargingthe acid ,slag making materials into the ladleeither before or duringthe charging of the molten steel is, furthermore, an intimate contact ofthe and the metal as to insure, tothe greatest extent possible, thewashing out of the oxids from the steel throughout the entire massthereof. Usually, it will not be found feasible to charge the steel fromthe open hearth or other furnace into the ladle without likewiseencumbering it .with a practically unavoidable proportion of the"furnace slag containing basic oxids; and, it will be understood that theamount of acid slag making materials to be charged into the ladle shouldbe sufficient to likewise balance and neutralize these basic oxids fromthe furnace. In fact, the quantity of acid slag making materials chargedinto the' ladle should be somewhat in excess of that required both forcleansing the steel from its contained oxids and also for balancing theoxide admitted from the furnace with the furnace slag, in order that thebody of slag finally floating upon the charged metal in the ladle shallbe devoid of any oxidizing effect upon the charge. In charging themolten steel into the ladle it will, of course, be understood that it ispreferable to avoid as far as possible the entrance of any large portionof the furnace slag. This may be effected in any suitable manner, as,for instain: by diverting the slag over; the side of the furnace spoutinto a slag receptacle.

Tilting furnaces may be used to advanfilled, the metal wlth tionof theslag andtage for the production of the steel, and the opening throughwhich the metal is ischarged from the furnace will be made of such sizeand the furnace so tilted during the pouring operation that the steelenters the ladle with but little slag, whereupon the slag may beafterward poured separately into another rece tacle. After the ladle isits rotecting top layer of acid slag is permitte to remain at rest for aperiod sufficient to insure the separametal, and is permitte to cool tothe temperature desirable for casting or teeming into the ingot molds.

In order to effect an entirely satisfactory cleansing of the metal inthe ladle, it should be at a relatively high temperature during thecleansing operation, as compared with the temperature of final pouringinto the ingot molds. For instance, the cleansing operation may becarried on with the metal at a temperature of say M00 C. to 14:50 O. Themetal in the ladle will preferably contain about 12% (if manganese anfrom .80% to 1.10% of carbon; and, in order to have as little piping aspossible in the ingots and to permit the metal to set without unduedelay in the molds, the metal in the ladle should be cooled, orpermitted to cool, before the pouring operation begins, to a temperatureof say 1875 C. The pouring from the ladle is effected through a bottompouring aperture, and the temperature 0 the metal and the attendantconditions'are tobe so established that the metal will set in the ingotmolds promptly, with the exception, perhaps, of a small proportion inthe innermost longitudinal center or core of the ingot.

While the ingot is still in the mold, I preferably cool it in suchmanner that, when stripped from the mold, the outer portions (to a depthfully including the thickness of the zone of the dendrites) will have anof 1000 0., (say from 950 C. to 1050 C.) except at the edges where itwill be unavoidably considerably lower. This enables it to betransferred, without suffering any rupture, into a soaking pit or otherfurnace, wherein it 18 to be subjected to the heat treatment designedfor reconstructing and it also permits its exterior portions;

take place without this heat treatment to cracking the ingot. tranceinto the soaking pit or like furnace, the ingot has set and developedits freezing structures to a depth of say siX inches ormore inwardlyfrom its outer skin or periphery and a zone of dendrites has formedwhich usually occupies say about one-half of this depth. In order tobreak down these dendrites and to substitute therefor a strong uniformstructure of fine grain, then slowly raise the temperature of thesoaking 1 average temperature in the neighborhood fit like heating 11 Atthe time of its en- 12 pit to 1l75 perature (for example 1225 C.) slowlyor evenly, this rise in temperature being efected in a smoky or reducingatmosphere, so that the periphery of the ingot will not be oxidized. Ihave found that with the pre liminary deoxidation and cleansing of theresult that the periphery metal, as hereinbefore described, the breakingdown of the dendrites and the substitution therefor of a strong uniformfine grained structure or about the temperature of 117 5 C. fied, withina comparatively of time, say half an hour, the temperature and the timeof reconstruction varying somewhat with the particular composition ofthe metal, but within relatively narrow limits, one way or the other,from the temperature and the period of half an hour referred to. I havealso found that, for steel of any given composition or analysis, thepreliminary deoxidizing and cleansing step permits the operator topredetermine the temperature and the time necessary for the desiredbreaking down of the dendrites and the reconstruction of the steel. Sothat,

specishort period C. or a somewhat higher tem not only is the periodreferred to shortened,

but the operation as a whole is so standardized that the desired resultcan be anticipated with confidence. After the ingot has remained at thetemperature of 1175 C. or thereabout for the period necessary for thereconstruction desired, this stage of the heat treatment is arrested bylowering the temperature so as to prevent the building up within themass of larger and coarser grains.

To this end, the temperature prevailing within the soaking pit or otherheating furnace may be lowered by the injection'of water vapor, in theform of a steamfjet, carrying with it water" in suspension, with the ofthe ingot is reduced in temperature to say 1100 C.; or for the samepurpose, the ingot may be cooled by transferring it into a coolersoaking pit, for example. The lowering of the "temperature of theexterior portions of the ingot is accompanied with the formation of atough thick skin, which shrinks upon and Works the ,still plasticinterior. Finally, after the cooling ofthe outer portions of the ingothas occurred, and the steam jet has been out off, the outer portionsofthe ingot are preferably permittedfto rise again in temperature to sayl125 (3., in order to equalize the surface temperaturesand to obtain thedesirable maximum ductility, whereupon the ingot maybe removed from thesoaking pit and is in condition tobe immediately rolled into rails orother products, in mills of ordinary construction. Moreover, thetemperature conditions are such that a track rail, for instance, ofstandard length and section, rolled from such an ingot, will bedelivered from the final pass nese steel of what may can be accomplishedat addition to this,

of the rolls at a temperature which will permit it to be toughened byquenching without being firstsubjected to a reheating operation.

I t will be understood that the cooling temperature of 1l 00 C. and thereheating temperature of 1125 C. referred to are not to be regarded asabsolute. They are the temperatures which are appropriate to mangabetermed a soft analysis, that is, having, say, 1.10% of carbon, or less,whereas, when the percentage of car bon is higher, say, 1.20%,tei'nperatnre of cooling will b'eisomewhat lower, and the temperature towhich the steel may be reheated will also be lower. In other words,these temperatures will depend upon the analysis of the steel,especially with regard to its content of carbon.

As hereinbefore stated, the preliminary step of deoxidizing andcleansing the manganese steel has for its effect not only to permit theshortening and' standardizing of the period in which the dendrites arebroken down andconverted into a uniform fine grained structure, but byclearing the metal of its oxids throughout, makes it correspondinglystrong as a final roduct and less tender during the inanipu ation towhich it is subjected from the time the ingot is cast until the rollingoperation is completed. In the preliminary deoxidation and cleansing ofthe metal and the f0rma-tion thereon of a tough thick skin by thecooling to which the ingot has been subjected after its period ofreconstruction, brings it into a larly appropriate to a still furtherconsolidation'and toughening of the skin by subjecting it to light itsperiphery. This light mechanical working has the effect of imparting tothe thick skin the characteristics of wrought metal, so that, whenthereafter subjected to heavy reductions incident to its passage throughthe 'rolls of the mill, it ,will have greater ductility and the dangerof rupture will be correspondingly lessened. The light mechanicalworking referred to will take place as a subsequent step to thecoolingoperation hereinbefore described, that is, immediately before theingot (after such cooling operation) would otherwise be rolled in theordinary mill.

The welding or consolidating of the outer portions of the ingot by thelight mechanical working described is of particular importance, wherethe mill work immediately following is heavy and where it involvessuddenreductions or rapid eiongations.

In order to the practice of the invention, I will assume that themanganese steel ingot is a 20" x 20 square section. The lightpreliminary rolland iv award, the

state or condition particumechanical Working over give aconcretei'nstance of the li ht )reluninar workin a ro riate to" s l y a:PP P ing would be ettected by actin first simultaneously upon twohorizontal sides, and then turning the ingot and acting simultaneouslyupon the two remaining sides. Where the analysis of the manganese steelof the ingot shows it to be low in warbon (say containing 1.10% of'arbon, or somewhat less than that amount), the reduction in the firston I or two passes of the preliminary light roiling may be about oneinch in each pass. This first reduction along the two horizontal sidesof the ingot renders the metal of those sides capable of greaterelongation, and consequently, when the ingot is turned over and rolledalong its opposite sides, a somewhat greater reduction can take place,say one and one-half or one an l. threepiarter inches. These twopreliminary reducing passes will in general sullice for the lightpreliminary rolling intended, although, 1n some instances, they may besupplemented by a third or even a fourth pass, if the mill conditionsare such that 'the light preliminary rolling can be effected quickly.When the manganese steel has a harder analysis, i. 0., when thepercentage of carbon is as high as 1.20%, or higher, it will usually beadvisable to limit the first reductions of the series of lightpreliminary passes to from one-half to three-quarters of an inch, itbeing permissible, however, to somewhat increase the reduction. in thesub sequent pass or passes, for the reason hereinbefore explained, e.,because the metal of those sides which have been subjected to the actionof the reducing rolls is capable of greater elongation for the nextsucceeding pass.

\Yhen an electric furnace is used for the making or compounding of themanganese steel, and when there is present in that furnace aconsiderable proportion of manganese, it is tillllClllt to avoid theproductionof a large amount of manganese oxid. To

meet this difiiculty, it will be desirable, just before the metal, istapped from the electric furnace into the ladle, to add to the furnacecharge a reducing agent (such as silico-calcium, aluminum,ferro-titaniuni, or the like) in sutlicient quantity to properly reducethe orids contained in the metal. The metal would then be charged intothe ladle, as free as possible from the furnace slag. in view of thehighly oxidizable character of the metal, further oxidation will takeplace dur ing the transfer of the metal from the furnace into the ladle,and therefore the final deoxidation, cleansing and washing of the steelwill proceed in the ladle as hereinbefore described. i

As has been hereinbc't'ore indicated, the twnperature of the ingot maybe raised in the soaking pit, in some instances, to a degree higher than1175- C. in its exterior portions; in fact, to somewhat exceed thislimit (say, by bringing the temperature of the exterior nations to 1225C.) will be found useful in most instances in order to insure greaterreliability in case the casting conditions should be more or lessunfavorable to the operation, and in order to obtain a corresprunlinglygreater ductility of the metal during its passage through the roll,

hat I. claim is:

1. in the production of manganese steel ingots and theirsubsequent heattreatment, in order to remove their objectionable freezing structures,the preliminary step of cleansing and deoxidizing the metal. 1' whichthe ingot is cast to an extent suilicici to sul'istantially eliminatevariations in the temperature necessary for the reconstruction desired,subjecting the ingot to a reoonstrncting temperature until theobjectionable freezing structures have been removed, and, after suchreconstrnctimi, lowering the temperature of the outer portions of theingot so as to avoid the production of large and coarse grains;substantially asdescrihed,

2. In the production. of manganese steel ingots and their subsequentheat treatment in order to remove their objectionable freezingstructures, the preliminary step of, cleansing and deoxidizing the metalfrom which the ingot is cast to an extent sutlicicin to substantiallyeliminate variations in the temperature necessary for the reconstructiondesired, casting the metal at a temperature but slightly above itsfreezing or setting point, subjecting the ingot to the recon structingtemperatureuntil the objectimiable "reezing structures have beenremoved, and, after such reconstruction, lowering the temperature of theouter portions of the ingot so as to avoid the production of large andcoarse grains; substantially "as described.

3. In the production of manganese steel. ingots and their subsequentheat treatment in order to convert their dendrites into structures ofuniform finegrain, the preliminary step of cleansing and deoxidizing themetal fronf which the ingot is cast to an extent sufficient tosubstantially eliminate variations in the temperature necessary for thereconstruction desired, subjecting the ingot to the reconstructingtemperature until the desired uniform tine crystalline structure hasbeen produced, and, after such recon-- struction, lowering thetemperature of the outer portions so as to avoid the production of largeand coarse grains; substantially as described.

4:. In the production of manganese steel ingots and their subsequentheat treatment in order to convert; their dendrites into struc tures ofuniform line grain, the preliminary step of cleansing and deoxidizingthe metal from which the ingot is *ast to an extent sufficient tosubstantially eliminate variations in the temperature necessary for theI desired, subjecting the ingot to the reconstructing "temperature untilthe desired uniform fine crystalline structure has been produced, and,after such reconstruction, lowering the temperature of the outerportions so as to avoid the production of large and coarse grains, andfinally lightly Working the outer portions of the ingot so as to producea wrought tough thick skin; substantially as described" 5. In theproduction of manganese steel ingots and their subsequent heattreatment, in order to remove their objectionable freezing s'tructures,.the preliminary step of cleansing and deoxidizing manganese steelcontaining about 12% Mn and about 1% C. from which the ingot is cast,the cleansreconstruction ing and deoxidati tent sufficient to on beingcarried to an exsubstantially eliminate variations in the temperaturenecessary for the bjecting theingot g temperature until theobjectionable freezing structures have been after such reconstruction,mperature of the outer por tions' of the ing otso as to avoid theproduction of large and coarse grains; substantially as described.

In testimony whereof I afiix my signature, in presence of two Witnesses.

Witnesses ELSA M. VVILLIAM 'WIN FIELD S. POTTER.

H. DAVIS.

